Rotor Bearing For A Laboratory Centrifuge

ABSTRACT

The locking system, which is intended to axially secure the rotor ( 1 ), of a laboratory centrifuge, wherein said rotor can be placed onto a rotatably mounted shaft ( 3 ) that extends vertically, is characterized by an arrangement of a plurality of locking levers ( 7 ), which are each pivotably mounted about axes ( 8 ) extending perpendicularly to the shaft ( 3 ) between a locking position and an unlocking position in planes containing the axes ( 2 ), wherein said locking levers can each be automatically transferred from the unlocking position to the locking position and from the locking position to the unlocking position depending on rotational speed. The locking levers ( 7 ) are mounted on the rotor ( 1 ), and an annular groove ( 6 ) is provided on the shaft ( 3 ), said annular groove engaging with the locking levers ( 7 ) in the locking position, wherein the locking levers ( 7 ) are prestressed in the unlocking position. An advantage over the prior art is achieved, namely that the rotor can be both installed and removed without tools by merely placing the rotor onto or removing the rotor from the shaft ( 3 ), in each case depending on rotational speed.

The invention relates to a rotor bearing for a laboratory centrifugecorresponding to the preamble of claim 1.

The rotor of such a laboratory centrifuge can be placed, within ahousing, from above onto the end of a shaft or of an assembly fixedlyconnected thereto, which assembly is connected to a centrifuge drive. Itis provided on the periphery with receivers intended for the insertionof vessels, into which the substances to be treated by centrifugationare received. Considering the high rotational speeds involved and therisk of accidents associated therewith, particular attention must begiven to providing a reliable and operationally secure seat for therotor on the shaft. Risks can arise owing to aerodynamic effects liftingthe rotor from the shaft within the centrifuge housing, but also by alateral impact thereon. Since different rotors are used, they areconnected to the shaft in an exchangeable manner, wherein the effort andtime required for mounting and removing a rotor can differ according tothe constructional design of locking means located between the rotor andthe shaft.

From the document WO 2010/025922 A1 a comparable rotor bearing is knownin which a sleeve comprising a conical inner profile can be placed ontoa vertically extending drive head comprising a complementarily conicalouter profile. The drive head is provided with an arrangement of axiallyparallel pins which, in the placed position, protrude into correspondingapertures in the rotor and are intended to exert an entraining effectabout the common axis of the rotor and drive head. The drive headfurther supports two mutually diametrically opposing coupling elementswhich can pivot about axes which are in parallel with each other andwith the axis of the drive head against the force of a return spring,and which coupling elements lie, when the rotor is stationary, on anannular surface of the said sleeve and even in this position form ameans of axially securing the placement position of the rotor. Theannular surface is formed in a conical manner and in particular underthe proviso that as the rotational speed of the rotor increases the saidinner and outer profiles are drawn against each other into increasinglyfirm contact. Although the rotor can be mounted without the use of toolsby mere placement onto the drive head, in order to remove it a pin-likeactuating element provided with a push button is required to transferthe coupling elements, which are active even in the stationarycondition, into a retracted position in which they no longer lie againstthe said annular surface. A not inconsiderable construction space isalso required to house the coupling elements, their return springs andthe actuating element.

On the basis of this background, the object of the invention is toimprove a rotor bearing of the type portrayed in the introduction in aconstructionally simple manner including with respect to asimplification of the rotor removal procedure. This object is achievedwith such a rotor bearing by the features of the characterizing part ofclaim 1.

The invention resides in the fact that both mounting and also removal ofthe rotor are achieved by placement onto the facing end of the shaft oreven of a component firmly connected thereto, and removal therefrom, andin particular without a tool being required or a manually operatedswitching member integrated into the rotor bearing. A rotor cantherefore be exchanged in the quickest and simplest manner, wherein theonly perquisite is that the rotor is stationary. For this purpose, alocking system is provided which consists of a plurality of lockinglevers which can pivot between a locking and an unlocking position inplanes which all contain the axes of the rotor and of the shaft. Thepivoting movement of the locking levers is initiated automatically andin particular in a rotational speed-dependent manner with thecooperation of centrifugal forces acting on the locking levers.

According to the features of claim 2 the pivoting movement of thelocking levers from the locking position into the unlocking position isalso initiated automatically in a rotational speed-dependent manneraccording to centrifugal forces acting on the locking lever.

An automatic rotational speed-dependent execution of a pivoting movementfrom the unlocking position to the locking position and vice versa can,in the simplest case, be brought about, for example, by a massdistribution of each locking lever relative to its pivot axis such thatby reason of gravity the unlocking position is a stable switchingposition into which the locking lever automatically tips when a definedrotational speed is no longer reached.

According to the features of claim 3, the bearing of the locking leversis preferably arranged on the rotor and they cooperate with an annulargroove which is disposed on the shaft or the component firmly connectedthereto. The engagement of the locking levers with this annular grooveprovides an axial means to prevent the rotor being pulled off. Thelocking levers are provided in the peripheral direction preferably in auniform distribution, which means that a uniform force transfer from therotor to the shaft is provided.

As long as sufficient installation space is available, the system oflocking levers can also be disposed on a component firmly connected tothe shaft and cooperate with an annular groove which can be worked intothe inner profile of the rotor.

According to the features of claims 4 and 5 an annular spring actingupon all the locking levers is provided, by means of which resilientpretensioning is provided, with which the unlocking position is secured.In this position all locking levers are therefore subject to the samemechanical pretensioning. The annular spring further effects—in arotational speed-dependent manner—the automatic transfer of all lockinglevers from the locking position into the unlocking position in whichthe rotor can easily be pulled axially off the shaft.

The features of claim 6 are directed at a variation of a locking leverwhich can indeed be transferred from the unlocking position into thelocking position in a rotational-speed dependent manner with theassistance of centrifugal forces, but wherein the locking position formsone stable switching position by reason of gravity and without theassistance of resilient forces and wherein the unlocking position formsthe other stable switching position by reason of resilient force. Suchbistable switching behavior of the locking lever can be achieved by acorresponding mass distribution relative to the pivot axis inconjunction with dimensioning and positioning, adapted thereto, of aspring element acting upon the locking lever. During acceleration of therotor the locking position is adopted by reason of centrifugal force andis retained during braking until the stationary condition. Pivoting intothe unlocking position can in this case be brought about merely bypulling off the rotor, whereby an entrainment effect can be exerted onthe locking levers and tilt them into the unlocking position.

According to the features of claim 7 each locking lever is mounted in anaperture in the rotor by means of a roller bearing.

According to the features of claim 8 each locking lever is fitted with acontrol body, the mass of which is determined under the proviso, and isso disposed relative to the axis thereof, that as a result of thecentrifugal forces acting thereon a pivoting movement is initiated fromthe unlocking position secured by resilient pretensioning towards thelocking position. The locking lever is for this purpose mounted in themanner of a two-sided lever, wherein the control body is located on oneside of the pivot axis thereof, by means of the mass and massdistribution of which control body relative to the pivot axis therotational speed-dependent pivoting characteristics can beconstructionally achieved under consideration of the resilientpretensioning.

The features of claims 9 and 10 are directed to the further design ofthe locking lever and of the said annular groove. The annular groove hasin each case a portion which is intended for contact on a locking edgeof the locking lever, wherein the locking edge is pressed against thisportion according to the centrifugal force acting on the control body,thus generating a force, during operation of the laboratory centrifuge,which draws the rotor downwards, i.e. against a contact surface of theshaft or of a component firmly connected thereto.

The features of claims 11 and 12 are directed at alternative embodimentsof the apertures in the locking levers which are intended to receive theannular spring. These apertures should be formed in such a way that easymounting of the annular spring is possible and furthermore it is ensuredthat unintentional movement of the annular spring out of these aperturesis reliably prevented. For this purpose, the aperture can be providedwith an insertion slit, i.e. it can be formed as a profile open in theperipheral direction. In this case, by means of the position and thedimensions of the slit, the annular spring is prevented from leaving theaperture. The aperture can, however, also be formed as a closed profile,which means that a spring present as a linear spring element in thestarting condition is threaded into these apertures one after the other,wherein the ends thereof are finally connected to each other to form anannular spring.

It will be recognized that with the present rotor bearing a particularlyeasy-to-handle operationally-safe embodiment is provided which makes itpossible to change a rotor in an extremely short time.

The invention will be described in more detail hereinunder withreference to the exemplified embodiment illustrated in the drawings inwhich:

FIG. 1 is a perspective, partial cross-sectional view of a rotor bearingin accordance with the invention;

FIG. 2 is a lateral view in a vertical cross-sectional plane of a rotorbearing in accordance with the invention;

FIG. 3 is a partially enlarged view of the rotor bearing according toFIG. 2 in the unlocking position;

FIG. 4 is a partially enlarged illustration of the rotor bearingaccording to FIG. 2 in the locking position;

FIG. 5 is an enlarged partial illustration V of FIG. 3;

FIG. 6 is an enlarged partial illustration VI of FIG. 3;

FIG. 7 is an enlarged partial illustration VII of FIG. 4;

FIG. 8 is an enlarged partial illustration VIII of FIG. 4;

FIG. 9 is a detail IX of FIG. 5;

FIG. 10 is a detail X of FIG. 4.

FIGS. 1 and 2 each show a rotor 1 of a laboratory centrifuge, which canbe placed onto the upper end of a shaft 3 mounted to be able to rotateabout an axis 2. The shaft 3 is connected to a drive in a manner notillustrated.

The rotor 1 is provided with apertures 4 in the peripheral region in amanner which is known per se, these apertures extend upwards at an anglein the direction of the axis 2 and are each arranged to receive vesselsintended for mixtures of substances to be treated by centrifugation.

On its upper end 5 intended for placement of the rotor 1, the shaft 3has a plurality of conically widening portions following one anotheraxially from the top to the bottom, wherein the inner profile of therotor 1 has portions adapted thereto. In particular, the outer profileof the shaft 3 has an annular groove 6 which is arranged for cooperationwith a locking system to be described hereinunder and which is intendedto secure a firm seat for the rotor 1 in the placement position, and inparticular during operation of the laboratory centrifuge.

The locking system consists of an arrangement of locking levers 7 whichare each mounted to be able to pivot about axes 8 in apertures 9 in theinner profile of the rotor 1, which extend perpendicular to the axis 2.A plurality of such locking levers 7 are provided in a uniformperipheral distribution, the axes of which all extend in a common planeperpendicular to the axis 2. Accordingly each locking lever 7 ispivotable in a plane in which the axis 2 is also located. In order toachieve a reproducible smooth pivoting movement of the locking levers 7,these are preferably mounted via roller bearings 15 within the apertures9.

Each locking lever 7 has, on its end facing the shaft 3, a locking edge10 which, in a manner yet to be described, is arranged and disposed forengagement with the annular groove 6.

Each locking lever 7 has, on its end opposite the locking edge 10, acylindrical control body 11. Finally, all locking levers 7 are connectedvia an annular spring 12 which is inserted into the respective aperture13 in each locking lever 7. The apertures 13 of the locking levers 7 aredisposed relative to the axes 8 under the proviso that when the rotor 1is stationary, a force holding all locking levers 7 in the unlockingposition illustrated in FIG. 3, can be exerted on the locking levers 7via the annular spring 12. This position is characterized in that thelocking edges 10 lie against the floor region 14 of the aperture 9,which in this respect fulfils a stop function, and at the same time arepivoted out of a region of engagement with the annular groove 6. Thisunlocking position is therefore secured by the annular spring 12.

If the rotor 1 is caused to rotate about the axis 2 via the shaft 3,then as a result of the centrifugal forces acting upon all controlbodies 11 when a defined rotational speed, constructionally preset bythe force of the annular spring 12, is exceeded a deflection of thelocking levers 7 about their axes 8 takes place, and in particular fromthe unlocking position shown in FIG. 3 into the locking position shownin FIG. 4, in which engagement of the locking edge 10 with the annulargroove 6 takes place.

In the locking position, which is automatically adopted in arotational-speed dependent manner, the axial position of the rotor 1 onthe shaft 3 is secured in a positive-fitting manner.

As shown in particular in FIGS. 5 to 8, the cross-sectional profile ofthe annular groove 6 consists of a first lower-side portion 16 whichextends upwards and—with respect to the axis of the shaft 3—inwards inan at least approximately rectilinear manner, to which a curved portion17 is attached which forms a contact edge for the locking edge 10 of thelocking lever 7.

In the operational state of the rotor 1 which, by reason of centrifugalforce, effects a rotation of the locking lever 7 from the unlockingposition shown in FIG. 5 in the clockwise direction about the axis 8 andin particular to a locking position characterized by the locking edge 10contacting the portion 17, a force drawing the rotor 1 downwards in thedirection of the arrow 18 onto the shaft 3 is produced, which means thatthe conical inner profile portions of the rotor 1 lie securely in aplay-free manner against the complementarily conical outer profileportions of the shaft 3.

As FIGS. 9, 10 show, the aperture 13 in each locking lever 7 ischaracterized by an insertion slit 19, via which the annular spring 12can be inserted into the aperture 13 of each locking lever 7. Theannular spring 12 can thus be mounted as an annular structure.

In the unlocking position shown in FIG. 9 the annular spring 12 liesagainst the radial inner side 20 of the aperture 13 and exerts a forcesecuring the locking lever 7, which lies on the floor region 14 of theaperture 9 in the rotor 1, in this position onto this lever. In thelocking position shown in FIG. 10, on the other hand, the annular spring12 is deflected in the outwards direction until coming into contact witha radial outer side 21 of the aperture 13.

As a result of the insertion slit 19, the cross-sectional profile of theaperture 13 forms at this point in each case a reduction incross-section which is dimensioned under the proviso that unintentionalor accidental exiting of the annular spring 12 from the aperture 13 byreason of centrifugal force is reliably prevented.

In practical terms the annular spring 12 can be designed as a wormspring 22 which on the inside carries a spring wire core 23 forstabilization purposes. A spring of this type can be used as a linearcomponent, the ends of which are connected to each other during mountingin order to form an annular structure. This offers the advantage thatinstead of the insertion slit 19 only bores or comparable apertureprofiles, which are closed on the peripheral side, intended to receivethe worm spring 22 are used. Radial exiting of the annular spring 12 byreason of centrifugal force is therefore reliably prevented.

It will be recognized from the statements above that the rotor bearingin accordance with the invention permits axial placement of the rotor 1onto the shaft 3 from above, wherein positive-fitting securing, inparticular locking, automatically occurs as a result of the rotation ofthe rotor 1, namely owing to the fact that the locking levers 7 comeinto engagement with the annular groove 6.

The locking state is also released automatically, namely as a result ofthe return force of the annular spring 12, as soon as a minimumrotational speed is no longer reached, which means that the lockinglevers 7 are automatically transferred into the unlocking position andthe rotor 1 can then be removed.

Reference list: 1 rotor 2 axis 3 shaft 4 aperture 5 upper end 6 annulargroove 7 locking lever 8 axis 9 aperture 10 locking edge 11 control body12 annular spring 13 aperture 14 floor region 15 roller bearing 16portion 17 portion 18 arrow 19 insertion slit 20 inner side 21 outerside 22 worm spring 23 spring wire core

1 Rotor bearing for a laboratory centrifuge, having a rotor (1) whichcan be placed onto a shaft (3) mounted so as to be able to rotate aboutan axis (2), having a locking system intended for axially securing therotor (1), characterized in that the locking system consists of anarrangement of locking levers (7) which are each mounted to be able topivot about axes (8) extending perpendicular to the axis (2) between alocking position and an unlocking position in planes containing the axis(2), which locking levers, in the locking position, axially fix therotor (1) with respect to the shaft (2) and that the locking levers (7)can be transferred automatically and in dependence upon the rotationalspeed at least from the unlocking position into the locking position. 2.Rotor bearing as claimed in claim 1, characterized in that the lockinglevers (7) can be transferred from the locking position into theunlocking position automatically in a rotational speed-dependent manner.3. Rotor bearing as claimed in claim 1, characterized in that thelocking levers (7) are mounted on the rotor (1) and that an annulargroove (6) is disposed on the shaft (3) and is arranged to cooperatewith the locking levers (7) in the locking position.
 4. Rotor bearing asclaimed in claim 1, characterized in that the locking levers (7) areunder resilient pretensioning in the unlocking position.
 5. Rotorbearing as claimed in claim 4, characterized in that in order to createthe resilient pretensioning an annular spring (12) is provided which isreceived in apertures (13) in the locking levers (7).
 6. Rotor bearingas claimed in claims 1, characterized in that the mass distribution ofeach locking lever (7) relative to the axis (8) is arranged under theproviso that the locking position is stable by reason of gravity andthat the unlocking position can be achieved by axial removal of therotor (1) from the shaft (3) with application of an entrainment effecton the locking lever (7).
 7. Rotor bearing as claimed in claim 1,characterized in that each locking lever (7) is pivotably mounted in anaperture (9) in the rotor (1) by means of a roller bearing (15). 8.Rotor bearing as claimed in claim 1, characterized in that a controlbody (11) to create the centrifugal force required to initiate thepivoting movement in the direction of the locking position is disposedon each locking lever (7). 9 Rotor bearing as claimed in claim 3,characterized in that a locking edge (10) is integrally formed on eachlocking lever (7) and is in engagement with the annular groove (6) inthe locking position. 10 Rotor bearing as claimed claim 3, characterizedin that the annular groove (6) has a rectilinear portion (16) intendedfor introduction of the facing end of the locking lever (7)and—adjoining this portion—a curved portion (17) intended for contactwith the facing end.
 11. Rotor bearing as claimed in claim 5,characterized in that each aperture (9) intended to receive the annularspring (12) has an insertion slit (19).
 12. Rotor bearing as claimed inclaim 5, characterized in that each aperture intended to receive theannular spring (12) has a profile which is closed on the peripheralside.
 13. Rotor bearing as claimed in claim 2 wherein the locking leversare mounted on the rotor and that an annular groove is disposed on theshaft and is arranged to cooperate with the locking levers in thelocking position.
 14. Rotor bearing as claimed in claim 2, wherein thelocking levers are under resilient pretensioning in the unlockingposition.
 15. Rotor bearing as claimed in claim 3, wherein the lockinglevers are under resilient pretensioning in the unlocking position. 16.Rotor bearing as claimed in claim 14, wherein in order to create theresilient pretensioning an annular spring is provided which is receivedin apertures in the locking levers.
 17. Rotor bearing as claimed inclaim 3, wherein the mass distribution of each locking lever relative tothe axis is arranged under the proviso that the locking position isstable by reason of gravity and that the unlocking position can beachieved by axial removal of the rotor from the shaft with applicationof an entrainment effect on the locking lever.
 18. Rotor bearing asclaimed in claim 2, wherein each locking lever is pivotably mounted inan aperture in the rotor by means of a roller bearing.
 19. Rotor bearingas claimed in claim 2, further comprising a control body to create thecentrifugal force required to initiate the pivoting movement in thedirection of the locking position is disposed on each locking lever. 20.Rotor bearing as claimed in claim 4, further comprising a locking edgeis integrally formed on each locking lever and is in engagement with theannular groove in the locking position.